Ring expansion is a chemical reaction in organic chemistry where a smaller cyclic compound is transformed into a larger cyclic compound by incorporating additional atoms or groups into the existing ring structure. This process often involves breaking existing bonds in the smaller ring and forming new bonds to create the larger ring. Ring expansion reactions can be useful in synthesizing complex organic molecules and are commonly employed in drug discovery and material science research. The mechanisms and conditions of ring expansion reactions can vary depending on the specific starting materials and desired products.